1. Field of the Invention.
The present invention relates to transmitters which produce an output as a function of a sensed parameter.
2. Description of the Prior Art.
Transmitters which sense a parameter and produce an output representing the sensed parameter have found widespread use in industrial process control systems. While most transmitters originally made use of analog electrical circuits, the development of low cost and low power digital electronics (and particularly microcomputer systems) has made it attractive to consider digital transmitters which perform at least some of the transmitter functions using digital circuitry.
Despite the increased attention given to digital transmitters, most sensors used for sensing common process control parameters (such as pressure and temperature) generate analog rather than digital sensor outputs. Digital transmitters which make use of analog sensor outputs need an analog-to-digital (A/D) converter to digitize the analog information. Because of power constraints, it is usually necessary to make trade-offs between output speed and output resolution in the circuit design of a digital transmitter. Typically these trade-offs will not satisfy all users, because some applications require fast response, while others require high resolution.